Direct acting solenoid actuators are often used to control fluid pressure in a variety of systems, including clutch mechanisms and other devices in an automobile. Direct acting solenoid actuators employ an armature mechanism that drives a fluid control element, such as a spool, a spring-biased four-way proportional flow control valve, a poppet valve, and the like in various hydraulic control applications. Typically, the armature is connected to, and drives, a push pin that engages the fluid control element to this end.
The fluid control element may comprise a spool surrounded by a valve body. The spool may be connected to the push pin such that any motion of the armature results in motion of the spool. The position of the spool, and the resulting fluid pressure, are directly dependent on the position of the armature. The coil, therefore, must produce a sufficiently strong magnetic field to move the spool under any pressure condition. To achieve this, the coil may require many loops, dictating the size of the apparatus and requiring a large quantity of copper wiring.